This interview with Aubrey de Grey and David Brin encapsulates the divide in longevity science. On the one side, people who see repair-based methodologies like SENS and the reversal of aging as the best way forward, and who foresee great progress within a few decades after major funding is achieved. On the other, people who look towards changing metabolism to slow aging, and who foresee little progress over the next few decades because the challenge of building a new, viable human metabolism is very, very hard. From de Grey's side of the article: "I think we have a 50% chance of achieving medicine capable of getting people to 200 in the decade 2030-2040. Presuming we do indeed do that, the actual achievement of 200 will probably be in the decade 2140-2150 - it will be someone who was about 85-90 at the time that the relevant therapies were developed. There will be no one technological breakthrough that achieves this. It will be achieved by a combination of regenerative therapies that repair all the different molecular and cellular degenerative components of aging." As a counterpoint, from Brin's side of the article: "I do not expect this any time soon. There are way too many obstacles. First, there is no low-hanging fruit. Simple switches, like the ones that are flipped in many animals, by caloric restriction or celibacy, are there to give creatures a delayed chance at reproduction, if it cannot happen earlier. These switches have already been thrown in humans. All of them! Because we had genuine darwinistic reasons to evolve longest possible lifespans. When the lore held by grandparents helped grandchildren to survive, we evolved a pattern where the tribe would always have a few grandparents around, who remembered stuff."